Intercellular Gap Junction Communication in the Bovine Annulus Fibrosus

Abstract

The intervertebral disc has a complex, anisotropic structure. The annulus fibrosus, the fibrous outer layer of the intervertebral disc, consists of fifteen to twenty-five concentric layers of collagen fibers at alternating orientations. Cells inside and between these lamellae are known to communicate with each other through gap junctions, protein channels that directly couple the membranes of adjacent cells and form interconnected networks that may be used to coordinate a response to mechanical stimuli. These fibroblastic cells fall into three distinct morphologies: spindle-shaped lamellar cells, round lamellar cells, and interlamellar cells. With confocal microscopy methods, gap-junctional intercellular signal propagation between groups of interconnected cells was examined. While the anisotropic microenvironment of the outer annulus was hypothesized to manifest in non-homogenous signal-propagation patterns, it was demonstrated that no clear directional biases or non-homogenous behavior existed among different cell morphologies and orientations; instead, intercellular signal propagation appears to be primarily proximity based.